In a semiconductor device manufacturing process, various treatments such as film formation, etching and the like are repeatedly performed on a substrate such as a semiconductor wafer or the like. In a semiconductor device manufacturing apparatus, a substrate processing system including a plurality of processing chambers is used. This substrate processing system includes one or more transfer units in order to carry out the transfer of a substrate within the system, e.g., between the processing chambers, and the transfer of a substrate to and from another substrate processing system.
Meanwhile, in the substrate processing system, as the treatment is repeated, reaction products are deposited on components or an inner wall of the processing chamber where the treatment such as film formation or the like is performed. The deposits are peeled off and become particles. The particles are adhered onto the substrate, so that the quality of the product deteriorates.
In order to remove the deposits, it is required to clean the inside of the processing chamber. For example, the processing chamber in which film formation is performed is cleaned by supplying a cleaning gas such as ClF3 gas, NF3 gas, Cl2 gas or the like into the processing chamber. After the cleaning is performed, pre-coating for depositing a thin film in the processing chamber is performed so that a following process can be performed under the same processing conditions. The combination of the cleaning and the pre-coating performed after the cleaning is referred to as “conditioning”. By performing the conditioning at a regular interval, the generation of particles can be prevented. The timing of executing the conditioning in the respective processing chambers of the substrate processing system varies in accordance with film forming conditions.
As for a method for controlling execution timing of the cleaning in the processing chamber, there has been proposed a method for detecting a contamination state of a processing chamber and determining whether or not cleaning needs to be executed based on a predetermined condition (e.g., Japanese Patent Application Publication No. 2003-277935).
In addition, there has been proposed a method that counts the number of execution of film formation in the processing chamber and performs pre-coating in the processing chamber when the number of execution of film formation exceeds a predetermined number so that the frequency of cleaning in the processing chamber can be reduced (e.g., Japanese Patent Application Publication No. 2006-351655).
In a multi-chamber type substrate processing system including a plurality of processing chambers, the conditioning is executed at different timings in the respective processing chambers. For example, in the processing chamber where film formation is performed, the conditioning is generally executed when the accumulated number of processed substrates or an accumulated film thickness reaches a predetermined level or when a contamination state is detected. Therefore, the execution timing of the conditioning is different in the respective processing chambers.
However, the state in which substrates in all processing chambers of the substrate processing system are simultaneously processed (hereinafter, may be referred to as “simultaneous use state of all processing chambers”) is continued for a long period of time, the transfers of substrates by transfer units cannot be carried out at desired timings. As a consequence, an idle time occurs in the processing chambers, and the productivity deteriorates.
For example, if the execution timing of the conditioning is the same in all processing chambers, the production in the substrate processing system is stopped for several hours.